Roland Hall, University of Waterloo

Roland Hall, University of Waterloo

With this in mind, Roland Hall from the University of Waterloo and colleagues measured metal concentrations in pre-industrial floodplain deposits and compared them with recently deposited river sediments.

In order to compare the floodplain deposits with the recent river sediments, Hall and colleagues normalised all the metal concentrations to lithium – a naturally-occurring metal that is not affected by human activities and so can be used to account for changes in contaminant concentrations due to variations in sediment grain size.

Of the 135 metal analyses, only three were at increased levels in recent river sediments, compared to the pre-industrial floodplain sediments. These were copper in 2010 and 2011, and chromium in 2013.

“For the other 132 river-bottom sediment measurements of various metals, including vanadium and other priority pollutants (Be, Cd, Pb, Ni, Zn, and most Cu and Cr samples), they all are at levels that correspond with natural baseline concentrations,” said Hall, whose findings are published in Environmental Research Letters (ERL).

Fort McMurray with Athabasca River-Courtesy: Wikipedia

Fort McMurray with Athabasca River-Courtesy: Wikipedia

This indicates the oil sands development has not increased metal pollution in downstream sediments in the Athabasca River. Instead the results suggest that the metals in the Athabasca River sediments are overwhelmingly supplied by natural sources. “They were likely derived from riverbank erosion, a natural process of metal delivery to downstream locations that has been taking place for thousands of years,” said Hall.